#include<iostream>
#include<iomanip>
#include<cmath>
using namespace std;
int main()
{int n,m;
 while(cin>>n>>m)
 {//if(n==0&&m==0) break;
  double c=m;
  if(m>=n/2)  m=n-m;
  double a=1,b=1;
  for (int i=1;i<=m;i++)
      a=a*i;
  for (int j=n;j>=n-m+1;j--)
      b=b*j;
  double sum=b/a;
  double d=floor(sum*1.f+0.5)/1.f;
  cout<<n<<" things taken "<<c<<" at a time is "<<setprecision(30)<<d<<" exactly."<<endl; 
 }
 system("pause");
 return 0;
}
